High rate method for stable temperature control of a substrate

ABSTRACT

A method for multi-step temperature control of a substrate includes selecting a first set-point temperature and a second set-point temperature for the substrate, and selecting a first PID parameter set including a first proportional constant K P1 , a first integral constant K I1  and a first derivative constant K D1 , and selecting a second PID parameter set including a second proportional constant K P2 , a second integral constant K I2  and a second derivative constant K D2 . The substrate is placed on a substrate holder, the temperature of the substrate is adjusted to the first set-point temperature and the substrate is processed for a first period of time at the first set-point temperature. The temperature of a region of the substrate is changed from the first set-point temperature to the second set-point temperature using the first PID parameter set for a first ramp period of time and using the second PID parameter set for a second ramp period of time, the second ramp period of time following the first ramp period of time. The substrate is then processed for a second period of time at the second set-point temperature.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending U.S. patent application Ser.No. 10/551,236, entitled “Method and System for Temperature Control of aSubstrate”, filed on Sep. 27, 2005; co-pending U.S. patent applicationSer. No. 11/525,818, entitled “High Temperature Substrate Holder for aSubstrate Processing System” (ES-108), filed on even date herewith;co-pending U.S. patent application Ser. No. 11/526,119, entitled “Methodfor Multi-step Temperature Control of a Substrate” (ES-112), filed oneven date herewith; and co-pending U.S. patent application Ser. No.11/525,815, entitled “High Temperature Substrate Holder withNon-homogeneous Insulation Layer for a Substrate Processing System”(ES-098), filed on even date herewith. The entire contents of theseapplications are herein incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for temperature control of asubstrate, and more particularly to a method of using a substrate holderfor temperature control of a substrate.

2. Description of Related Art

It is known in semiconductor manufacturing and processing that variousprocesses, including for example etch and deposition processes, dependsignificantly on the temperature of the substrate. For this reason, theability to control the temperature of a substrate and controllablyadjust the temperature of the substrate is becoming an essentialrequirement of a semiconductor processing system. The temperature of asubstrate is determined by many processes including, but not limited to,substrate interaction with plasma, chemical processes, etc., as well asradiative and/or conductive thermal exchange with the surroundingenvironment. Providing a proper temperature to the upper surface of thesubstrate holder can be utilized to control the temperature of thesubstrate.

SUMMARY OF THE INVENTION

The present invention relates to a system for controlling thetemperature of a substrate.

According to one embodiment, a method of using a substrate support isdescribed, the substrate support comprising one or more heating elementsseparated from one or more cooling elements by a thermal insulator.

According to another embodiment, a method for controlling thetemperature of a substrate in a substrate processing system isdescribed, the substrate processing system including a substrate holderfor supporting the substrate and having a temperature sensor reporting atemperature at a region of the substrate and a heating element heatingthe region and being controlled by a temperature control system tocontrol the temperature of the substrate using a PID control algorithm.The method includes selecting a first set-point temperature, selecting asecond set-point temperature, selecting a first PID parameter setincluding a first proportional constant K_(P1), a first integralconstant K_(I1) and a first derivative constant K_(D1), and selecting asecond PID parameter set including a second proportional constantK_(P2), a second integral constant K_(I2) and a second derivativeconstant K_(D2). The substrate is placed on the substrate holder, thetemperature of the substrate is adjusted to the first set-pointtemperature and the substrate is processed for a first period of time atthe first set-point temperature. The temperature of the region of thesubstrate is changed from the first set-point temperature to the secondset-point temperature using the first PID parameter set for a first rampperiod of time and using the second PID parameter set for a second rampperiod of time, the second ramp period of time following the first rampperiod of time. The substrate is then processed for a second period oftime at the second set-point temperature.

According to yet another embodiment, a method for controlling thetemperature of a substrate in a substrate processing system isdescribed, the substrate processing system including a substrate holderfor supporting the substrate and having a plurality of temperaturesensors reporting at least a temperature at an inner region and an outerregion of the substrate, and first and second heating elements heatingrespectively the inner region and the outer region, the first and secondheating elements being controlled by a temperature control system usinga PID controller to maintain the substrate holder at a selectableset-point temperature. The method includes selecting a first innerset-point temperature and a first outer set-point temperature, selectinga second inner set-point temperature and a second outer set-pointtemperature, selecting a first inner PID parameter set including a firstinner proportional constant K_(Pinner1), a first inner integral constantK_(Iinner1) and a first inner derivative constant K_(Dinner1), selectinga second inner PID parameter set including a second inner proportionalconstant K_(Pinner2), a second inner integral constant K_(Iinner2) and asecond inner derivative constant K_(Dinner2). Also included is selectinga first outer PID parameter set including a first outer proportionalconstant K_(Pouter1), a first outer integral constant K_(Iouter1) and afirst outer derivative constant K_(Douter1); selecting a second outerPID parameter set including a second outer proportional constantK_(Pouter2), a second outer integral constant K_(Iouter2) and a secondouter derivative constant K_(Douter2). The substrate is placed on thesubstrate holder and the inner region of the substrate is heated to thefirst inner set-point temperature and the outer region of the substrateis heated to the first outer set-point temperature, and the substrate isprocessed for a first period of time at the first inner and outerset-point temperatures. The temperature of the inner region of thesubstrate is changed from the first inner set-point temperature to thesecond inner set-point temperature using the first inner PID parameterset for a first inner ramp period of time and using the second inner PIDparameter set for a second inner ramp period of time, the second innerramp period of time following the first inner ramp period of time, andthe temperature of the outer region of the substrate is changed from thefirst outer set-point temperature to the second outer set-pointtemperature using the first outer PID parameter set for a first outerramp period of time and using the second outer PID parameter set for asecond outer ramp period of time, the second outer ramp period of timefollowing the first outer ramp period of time. The substrate is thenprocessed for a second period of time at the second inner and outerset-point temperatures.

Another aspect of the invention includes a method of changing thetemperature of a substrate during processing of the substrate. Themethod includes providing the substrate on a substrate holder, thesubstrate holder including a temperature controlled substrate supportfor supporting the substrate, a temperature controlled base support forsupporting the substrate support and a thermal insulator interposedbetween the temperature controlled substrate support and the temperaturecontrolled base support. The method also includes setting thetemperature of the base support to a first base temperaturecorresponding to a first processing temperature of said substrate,setting the substrate support to a first support temperaturecorresponding to said first processing temperature of said substrate andsetting the temperature of the base support to a second base temperaturecorresponding to a second processing temperature of said substrate. Thesubstrate support temperature is then changed to a second supporttemperature corresponding to said second processing temperature of saidsubstrate by selecting a first PID parameter set including a firstproportional constant K_(P1), a first integral constant K_(I1) and afirst derivative constant K_(D1), selecting a second PID parameter setincluding a second proportional constant K_(P2), a second integralconstant K_(I2) and a second derivative constant K_(D2), and changingthe temperature of said substrate from said first set-point temperatureto said second set-point temperature using said first PID parameter setfor a first ramp period of time and using said second PID parameter setfor a second ramp period of time, said second ramp period of timefollowing said first ramp period of time.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 presents a block diagram of a substrate processing systemaccording to an embodiment of the present invention;

FIG. 2A presents a schematic cross-section view of a substrate holderaccording to an embodiment of the present invention;

FIG. 2B illustrate exemplary profiles in thermal conductivity andsubstrate temperature for a substrate holder;

FIG. 3 presents a schematic cross-section view of a substrate holderaccording to another embodiment of the present invention;

FIG. 4 presents a schematic cross-section view of a substrate holderaccording to another embodiment of the present invention;

FIG. 5 presents a schematic cross-section view of a substrate holderaccording to another embodiment of the present invention;

FIG. 6 presents a schematic cross-section view of a substrate holderaccording to another embodiment of the present invention;

FIGS. 7A and 7B illustrate exemplary time traces of temperature; and

FIG. 8 illustrates a flow chart of a method of adjusting a substratetemperature according to an embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the following description, for purposes of explanation and notlimitation, specific details are set forth, such as a particulargeometry of the substrate holder for a substrate processing system anddescriptions of various components and processes. However, it should beunderstood that the invention may be practiced in other embodiments thatdepart from these specific details.

According to an embodiment of the present invention, a materialprocessing system 1 is depicted in FIG. 1 that includes a process tool10 having a substrate holder 20 and a substrate 25 supported thereon.The substrate holder 20 is configured to provide temperature controlelements for adjustment of substrate temperature. Additionally, thetemperature control elements may be spatially arranged in order toensure a uniform or non-uniform substrate temperature. A controller 55is coupled to the process tool 10 and the substrate holder 20, and isconfigured to monitor, adjust and control the substrate temperature aswill be further discussed below.

In the illustrated embodiment depicted in FIG. 1, the materialprocessing system 1 can include an etch chamber. For example, the etchchamber can facilitate dry plasma etching, or, alternatively, drynon-plasma etching. Alternately, the material processing system 1includes a photo-resist coating chamber such as a heating/cooling modulein a photo-resist spin coating system that may be utilized forpost-adhesion bake (PAB) or post-exposure bake (PEB), etc.; aphoto-resist patterning chamber such as a photo-lithography system; adielectric coating chamber such as a spin-on-glass (SOG) orspin-on-dielectric (SOD) system; a deposition chamber such as a vapordeposition system, chemical vapor deposition (CVD) system, plasmaenhanced CVD (PECVD) system, atomic layer deposition (ALD) system,plasma enhanced ALD (PEALD) system, or a physical vapor deposition (PVD)system; or a rapid thermal processing (RTP) chamber such as a RTP systemfor thermal annealing.

Referring now to FIG. 2A, a substrate holder is described according toone embodiment. The substrate holder 100 comprises a substrate support130 having a first temperature and configured to support a substrate110, a temperature-controlled support base 120 positioned belowsubstrate support 130 and configured to be at a second temperature lessthan the first temperature (e.g. less than a desired temperature ofsubstrate 110), and a thermal insulator 140 disposed between thesubstrate support 130 and the temperature-controlled support base 120.Additionally, the substrate support 130 comprises one or more heatingelements coupled thereto (not shown), and configured to elevate thetemperature of the substrate support 130 (e.g. to heat the substrate).It is to be understood that the first temperature may be part of atemperature gradient across the substrate support and the secondtemperature may be part of a temperature gradient across the temperaturecontrolled base according to embodiments of the invention.

According to one embodiment, the thermal insulator 140 comprises athermal conductivity lower than the respective thermal conductivities ofboth the substrate support 130 and the temperature-controlled supportbase 120. For example, the thermal conductivity of the thermal insulator140 is less than 1 W/m-K. Desirably, the thermal conductivity of thethermal insulator ranges from approximately 0.05 W/m-K to approximately0.8 W/m-K and, more desirably, the thermal conductivity of the thermalinsulator ranges from approximately 0.2 W/m-K to approximately 0.8W/m-K.

The thermal insulator 140 can comprise an adhesive made of polymer,plastic or ceramic. The thermal insulator 140 may include an organic oran inorganic material. For example, the thermal insulator 140 cancomprise a room-temperature-vulcanizing (RTV) adhesive, a plastic suchas a thermoplastic, a resin such as a thermosetting resin or a castingresin (or pourable plastic or elastomer compound), an elastomer, etc. Inaddition to providing a thermal resistance between the substrate support130 and the temperature-controlled support base 120, the thermalinsulator 140 may provide a bond layer or adhesion layer between thesubstrate support 130 and the temperature-controlled support base 120.

The thickness and material composition of the thermal insulator 120should be selected such that, when necessary, adequate radio frequency(RF) coupling between the support base 120 and plasma can be maintained.Furthermore, the thermal insulator 120 should be selected in order totolerate thermal-mechanical shear driven by thermal gradients anddifferences in material properties, i.e., coefficient of thermalexpansion. For example, the thickness of the thermal insulator 140 canbe less than or equal to approximately 10 mm (millimeters), anddesirably, the thickness can be less than or equal to approximately 5mm, i.e., approximately 2 mm or less.

Additionally, the material composition of the thermal insulator 140 ispreferably such that it demonstrates erosion resistance to theenvironment within which it is utilized. For example, when presentedwith a dry plasma etching environment, the thermal insulator 140 shouldbe resistant to the corrosive etch chemistries used during the etchingprocess, as well as the corrosive cleaning chemistries used during anetch system cleaning process. In many etching chemistries and cleaningchemistries, halogen-containing process gases are utilized including,but not limited to, Cl₂, F₂, Br₂, HBr, HCl, HF, SF₆, NF₃, ClF₃, etc. Inthese chemistries, particularly cleaning chemistries, it is desirable toproduce high concentrations of reactive atomic halogen species, such asatomic fluorine, etc.

According to one embodiment, the thermal insulator 140 comprises anerosion resistant thermal insulator. In one embodiment, the entirethermal insulator is made from the erosion resistant material.Alternatively, only a portion of the thermal insulator 140, such asportions exposed to halogen-containing gas, can include the erosionresistant material. For example, the erosion resistant material may beincluded only at a peripheral exposed edge of the thermal insulator,while the remaining region of the thermal insulator includes a differentmaterial composition selected for providing a desired heat transferco-efficient.

The erosion resistant thermal insulator can include an acryl-typematerial, such as an acrylic-based material or an acrylate-basedmaterial. Acrylic-based materials and acrylate-based materials can beformed by polymerizing acrylic or methylacrylic acids through a reactionwith a suitable catalyst. Table 1 provides data illustrating thedependence of erosion resistance on material composition. For example,data is provided for silicon-containing adhesives, and a series ofacrylic/acrylate-containing adhesives (prepared by various vendors X, Y,Z, Q, R & T). The data includes the erosion amount (mm³) as a functionof plasma (or RF power on) hours (hr); i.e, mm³/hr. As shown in Table 1,the acrylic/acrylate-containing adhesives exhibit more than an order ofmagnitude less erosion when subjected to a cleaning plasma (such as aSF₆-based plasma).

TABLE 1 Silicon Acryl type type X Y Z Q R T Thickness (mm) 0.13 0.130.25 0.13 0.15 0.05 0.12 Thermal 0.25 0.35 0.6 0.37 0.3 0.6 0.2conductivity (W/m-K) Thermal resistance 5.2 3.7 4.2 3.5 7.5 8.3 6 (E⁻⁴)Erosion ratio 5.5 0.32 0.3 0.22 0.25 0.15 0 (mm³/hr)

According to yet another embodiment, the thermal insulator 140 comprisesa non-uniform spatial variation of the heat transfer coefficient(W/m²-K) through the thermal insulator 140 between the temperaturecontrolled support base 120 and the substrate support 130. For example,the heat transfer coefficient can vary in a radial direction between asubstantially central region of the thermal insulator 140 (belowsubstrate 110) and a substantially edge region of the thermal insulator140 (below substrate 110). The spatial variation of the heat transfercoefficient may comprise a non-uniform spatial variation of the thermalconductivity (W/m-K) of the thermal insulator 140, or the spatialvariation of the heat transfer coefficient may comprise a non-uniformspatial variation of the thickness of the thermal insulator 140, orboth. As used herein, the term “non-uniform spatial variation” of aparameter means a spatial variation of the parameter across an area ofthe substrate holder that is caused by design rather than inherent minorvariations of the parameter across a substrate holder. Further, the term“substantially central region of the thermal insulator” means a regionof the thermal insulator that would overlap a center of the substrate ifplaced on the substrate holder, and the term “substantially edge regionof the thermal insulator” means a region of the thermal insulator thatwould overlap an edge of the substrate if placed on the substrateholder.

As illustrated in FIG. 2B, the thermal conductivity can vary in a radialdirection between a substantially central region of the thermalinsulator 140 below substrate 110 and a substantially edge region of thethermal insulator 140 below substrate 110. For example, the thermalconductivity can vary between a first value between approximately 0.2W/m-K and approximately 0.8 W/m-K and a second value betweenapproximately 0.2 W/m-K and approximately 0.8 W/m-K. Additionally, forexample, the thermal conductivity can be approximately 0.2 W/m-K near asubstantially central region of the thermal insulator 140 and thethermal conductivity can be approximately 0.8 W/m-K near a substantiallyedge region of the thermal insulator 140 . Additionally yet, forexample, the variation in the thermal conductivity substantially occursbetween approximately the mid-radius region of the thermal insulator 140and a substantially peripheral region of the thermal insulator 140 . Asshown in FIG. 2B, the temperature may vary from center to edge between afirst temperature (T₁) and a second temperature (T₂). Such variations inthermal conductivity (and temperature) may be imposed to counterexcessive heating of the peripheral edge of the substrate by, forinstance, the focus ring surrounding the substrate.

As illustrated in FIG. 3, a substrate holder is described according toanother embodiment. The substrate holder 200 comprises a substratesupport 230 having a first temperature and configured to support asubstrate 210, a temperature-controlled support base 220 positionedbelow substrate support 230 and configured to be at a second temperatureless than the first temperature (e.g. less than a desired temperature ofsubstrate 210), and a thermal insulator 240 disposed between thesubstrate support 230 and the temperature-controlled support base 220.Additionally, the substrate support 230 comprises one or more heatingelements coupled thereto (not shown), and configured to elevate thetemperature of the substrate support 230 (e.g. to heat the substrate).The thermal insulator 240 comprises a non-uniform thickness.

As shown, the thickness is less at a substantially center region of thethermal insulator 240 (below substrate 210) and it is relatively thickerat a substantially edge region below the substrate 210. Alternatively,the thickness can be greater at a substantially center region belowsubstrate 210 and it can be relatively thinner at a substantially edgeregion of substrate 210. The non-uniform thickness of thermal insulator240 may be imposed by a non-flat upper surface on support base 220, orit may be imposed by a non-flat lower surface of substrate support 240,or it may be imposed by a combination thereof. Alternatively yet, alayer of material having a different thermal conductivity than that ofthe thermal insulator 240 may be disposed on a portion of either theupper surface of support base 220 or the lower surface of substratesupport 230. For instance, a layer of Kapton®, Vespel®, Teflon®, etc.,may be disposed on a substantially central region below substrate 210,or such a layer may be disposed on a substantially peripheral regionbelow substrate 210.

Referring now to FIG. 4, a substrate holder is described according toanother embodiment. The substrate holder 300 comprises a substratesupport 330 having a first temperature and configured to support asubstrate 310, a temperature-controlled support base 320 positionedbelow substrate support 330 and configured to be at a second temperatureless than the first temperature (e.g. less than a desired temperature ofsubstrate 310), and a thermal insulator 340 disposed between thesubstrate support 330 and the temperature-controlled support base 320.Additionally, the substrate support 330 comprises one or more heatingelements coupled thereto (not shown), and configured to elevate thetemperature of the substrate support 330.

As shown in FIG. 4, the support base 320 comprises a plurality ofprotrusions, or ridges 342, that partially extend into (or fully extendthrough) the thermal insulator 340. Furthermore, the number density ofprotrusions can vary between a substantially central region 344 and asubstantially peripheral region 346 of the substrate holder. Forexample, a higher density of protrusions may be placed at the peripheralregion 346, while a relatively lower density of protrusions may beplaced at the central region 344. Alternatively, for example, a lowerdensity of protrusions may be placed at the peripheral region 346, whilea relatively higher density of protrusions may be placed at the centralregion 344. In addition to the variation in density of protrusions, orin lieu of a variation in density, the size or shape or both of theprotrusions may be varied.

The temperature controlled support base 120 (220, 320) may be fabricatedfrom a metallic material or a non-metallic material. For example, thesupport base 120 (220, 320) can be fabricated from aluminum.Additionally, for example, the support base 120 (220, 320) can be formedof a material having a relatively high thermal conductivity, such thatthe temperature of the support base can be maintained at a relativelyconstant temperature. The temperature of the temperature controlledsupport base is preferably actively controlled by one or moretemperature control elements such as cooling elements. However, thetemperature controlled support may provide passive cooling by use ofcooling fins to promote enhanced free convection due to the increasedsurface area with the surrounding environment for example. The supportbase 120 (220, 320) can further include passages therethrough (notshown) to permit the coupling of electrical power to the one or moreheating elements of the substrate support, the coupling of electricalpower to an electrostatic clamping electrode, the pneumatic coupling ofheat transfer gas to the backside of the substrate, etc.

The substrate support 130 (230, 330) may be fabricated from a metallicmaterial or a non-metallic material. The substrate support 130 (230,330) can be fabricated from a non-electrically conductive material, suchas a ceramic. For example, substrate support 130 (230, 330) can befabricated from alumina.

According to one embodiment, the one or more heating elements areembedded within the substrate support 130 (230, 330). The one or moreheating elements can be positioned between two ceramic pieces which aresintered together to form a monolithic piece. Alternatively, a firstlayer of ceramic is thermally sprayed onto the thermal insulator,followed by thermally spraying the one or more heating elements onto thefirst ceramic layer, and followed by thermally spraying a second ceramiclayer over the one or more heating elements. Using similar techniques,other electrodes, or metal layers, may be inserted within the substratesupport 130 (230, 330). For example, an electrostatic clamping electrodemay be inserted between ceramic layers and formed via sintering orspraying techniques as described above. The one or more heating elementsand the electrostatic clamping electrode may be in the same plane or inseparate planes, and may be implemented as separate electrodes orimplemented as the same physical electrode.

Referring now to FIG. 5, a substrate holder is described according toanother embodiment. The substrate holder 400 comprises a substratesupport 430 having a first temperature and configured to support asubstrate 410, a temperature-controlled support base 420 positionedbelow substrate support 430 and configured to be at a second temperatureless than the first temperature (e.g. less than a desired temperature ofsubstrate 410), and a thermal insulator 440 disposed between thesubstrate support 430 and the temperature-controlled support base 420.Additionally, the substrate support 430 comprises one or more heatingelements 431 coupled thereto, and configured to elevate the temperatureof the substrate support 430. Furthermore, the support base 420comprises one or more cooling elements 421 coupled thereto, andconfigured to reduce the temperature of the substrate support 430 viathe removal of heat from the substrate support 430 through thermalinsulator 440.

The one or more heating elements 431 can comprise at least one of aheating fluid channel, a resistive heating element, or a thermoelectricelement biased to transfer heat towards the wafer. Furthermore, as shownin FIG. 5, the one or more heating elements 431 are coupled to a heatingelement control unit 432. Heating element control unit 432 is configuredto provide either dependent or independent control of each heatingelement, and exchange information with a controller 450.

For example, the one or more heating elements 431 can comprise one ormore heating channels that can permit a flow rate of a fluid, such aswater, Fluorinert, Galden HT-135, etc., therethrough in order to provideconductive-convective heating, wherein the fluid temperature has beenelevated via a heat exchanger. The fluid flow rate and fluid temperaturecan, for example, be set, monitored, adjusted, and controlled by theheating element control unit 432.

Alternatively, for example, the one or more heating elements 431 cancomprise one or more resistive heating elements such as a tungsten,nickel-chromium alloy, aluminum-iron alloy, aluminum nitride, etc.,filament. Examples of commercially available materials to fabricateresistive heating elements include Kanthal, Nikrothal, Akrothal, whichare registered trademark names for metal alloys produced by KanthalCorporation of Bethel, Conn. The Kanthal family includes ferritic alloys(FeCrAl) and the Nikrothal family includes austenitic alloys (NiCr,NiCrFe). For example, the heating elements can comprise a cast-in heatercommercially available from Watlow (1310 Kingsland Dr., Batavia, Ill.,60510) capable of a maximum operating temperature of 400 to 450 C, or afilm heater comprising aluminum nitride materials that is alsocommercially available from Watlow and capable of operating temperaturesas high as 300 C and power densities of up to 23.25 W/cm². Additionally,for example, the heating element can comprise a silicone rubber heater(1.0 mm thick) capable of 1400 W (or power density of 5 W/in²). When anelectrical current flows through the filament, power is dissipated asheat, and, therefore, the heating element control unit 432 can, forexample, comprise a controllable DC power supply. A further heateroption, suitable for lower temperatures and power densities, are Kaptonheaters, consisted of a filament embedded in a Kapton (e.g. polyimide)sheet, marketed by Minco, Inc., of Minneapolis, Minn.

Alternately, for example, the one or more heating elements 431 cancomprise an array of thermoelectric elements capable of heating orcooling a substrate depending upon the direction of electrical currentflow through the respective elements. Thus, while the elements 431 arereferred to as “heating elements,” these elements may include thecapability of cooling in order to provide rapid transition betweentemperatures. Further, heating and cooling functions may be provided byseparate elements within the substrate support 430. An exemplarythermoelectric element is one commercially available from AdvancedThermoelectric, Model ST-127-1.4-8.5M (a 40 mm by 40 mm by 3.4 mmthermoelectric device capable of a maximum heat transfer power of 72 W).Therefore, the heating element control unit 432 can, for example,comprise a controllable current source.

The one or more cooling elements 421 can comprise at least one of acooling channel, or a thermoelectric element. Furthermore, as shown inFIG. 5, the one or more cooling elements 421 are coupled to a coolingelement control unit 422. Cooling element control unit 422 is configuredto provide either dependent or independent control of each coolingelement 421, and exchange information with controller 450.

For example, the one or more cooling elements 421 can comprise one ormore cooling channels that can permit a flow rate of a fluid, such aswater, Fluorinert, Galden HT-135, etc., therethrough in order to provideconductive-convective cooling, wherein the fluid temperature has beenlowered via a heat exchanger. The fluid flow rate and fluid temperaturecan, for example, be set, monitored, adjusted, and controlled by thecooling element control unit 422. Alternately, during heating forexample, the fluid temperature of the fluid flow through the one or morecooling elements 421 may be increased to complement the heating by theone or more heating elements 431. Alternately yet, during cooling forexample, the fluid temperature of the fluid flow through the one or morecooling elements 421 may be decreased.

Alternately, for example, the one or more cooling elements 421 cancomprise an array of thermoelectric elements capable of heating orcooling a substrate depending upon the direction of electrical currentflow through the respective elements. Thus, while the elements 421 arereferred to as “cooling elements,” these elements may include thecapability of heating in order to provide rapid transition betweentemperatures. Further, heating and cooling function may be provided byseparate elements within the temperature controlled support base 420. Anexemplary thermoelectric element is one commercially available fromAdvanced Thermoelectric, Model ST-127-1.4-8.5M (a 40 mm by 40 mm by 3.4mm thermo-electric device capable of a maximum heat transfer power of 72W). Therefore, the cooling element control unit 422 can, for example,comprise a controllable current source.

Additionally, as shown in FIG. 5, the substrate holder 400 can furthercomprise an electrostatic clamp (ESC) comprising one or more clampingelectrodes 435 embedded within substrate support 430. The ESC furthercomprises a high-voltage (HV) DC voltage supply 434 coupled to theclamping electrodes 435 via an electrical connection. The design andimplementation of such a clamp is well known to those skilled in the artof electrostatic clamping systems. Furthermore, the HV DC voltage supply434 is coupled to controller 450 and is configured to exchangeinformation with controller 450.

Furthermore, as shown in FIG. 5, the substrate holder 400 can furthercomprise a back-side gas supply system 436 for supplying a heat transfergas, such as an inert gas including helium, argon, xenon, krypton, aprocess gas, or other gas including oxygen, nitrogen, or hydrogen, tothe backside of substrate 410 through at least one gas supply line, andat least one of a plurality of orifices and channels (not shown). Thebackside gas supply system 436 can, for example, be a multi-zone supplysystem such as a two-zone (center/edge) system, or a three-zone(center/mid-radius/edge), wherein the backside pressure can be varied ina radial direction from the center to edge. Furthermore, the backsidegas supply system 436 is coupled to controller 450 and is configured toexchange information with controller 450.

Further yet, as shown in FIG. 5, the substrate holder 400 can furthercomprise one or more temperature sensors 462 coupled to a temperaturemonitoring system 460. The one or more temperature sensors 462 can beconfigured to measure the temperature of substrate 410, or the one ormore temperature sensors 462 can be configured to measure thetemperature of substrate support 430, or both. For example, the one ormore temperature sensors 410 may be positioned such that the temperatureis measured at the lower surface of the substrate support 430 as shownin FIG. 5, or positioned such that the temperature of a bottom of thesubstrate 410 is measured.

The temperature sensor can include an optical fiber thermometer, anoptical pyrometer, a band-edge temperature measurement system asdescribed in pending U.S. patent application Ser. No. 10/168544, filedon Jul. 2, 2002, the contents of which are incorporated herein byreference in their entirety, or a thermocouple (as indicated by thedashed line) such as a K-type thermocouple. Examples of opticalthermometers include: an optical fiber thermometer commerciallyavailable from Advanced Energies, Inc., Model No. OR2000F; an opticalfiber thermometer commercially available from Luxtron Corporation, ModelNo. M600; or an optical fiber thermometer commercially available fromTakaoka Electric Mfg., Model No. FT-1420.

The temperature monitoring system 460 can provide sensor information tocontroller 450 in order to adjust at least one of a heating element, acooling element, a backside gas supply system, or an HV DC voltagesupply for an ESC either before, during, or after processing.

Controller 450 includes a microprocessor, memory, and a digital I/O port(potentially including D/A and/or A/D converters) capable of generatingcontrol voltages sufficient to communicate and activate inputs tosubstrate holder 400 as well as monitor outputs from substrate holder400. As shown in FIG. 5, controller 450 can be coupled to and exchangeinformation with heating element control unit 432, cooling elementcontrol unit 422, HV DC voltage supply 434, backside gas supply system436, and temperature monitoring system 460. A program stored in thememory is utilized to interact with the aforementioned components ofsubstrate holder 400 according to a stored process recipe. One exampleof controller 450 is a DELL PRECISION WORKSTATION 640™, available fromDell Corporation, Austin, Tex.

The controller 450 may also be implemented as a general purposecomputer, processor, digital signal processor, etc., which causes asubstrate holder to perform a portion or all of the processing steps ofthe invention in response to the controller 450 executing one or moresequences of one or more instructions contained in a computer readablemedium. The computer readable medium or memory is configured to holdinstructions programmed according to the teachings of the invention andcan contain data structures, tables, records, or other data describedherein. Examples of computer readable media are compact discs, harddisks, floppy disks, tape, magneto-optical disks, PROMs (EPROM, EEPROM,flash EPROM), DRAM, SRAM, SDRAM, or any other magnetic medium, compactdiscs (e.g., CD-ROM), or any other optical medium, punch cards, papertape, or other physical medium with patterns of holes, a carrier wave,or any other medium from which a computer can read.

Controller 450 may be locally located relative to the substrate holder400, or it may be remotely located relative to the substrate holder 400via an internet or intranet. Thus, controller 450 can exchange data withthe substrate holder 400 using at least one of a direct connection, anintranet, or the internet. Controller 450 may be coupled to an intranetat a customer site (i.e., a device maker, etc.), or coupled to anintranet at a vendor site (i.e., an equipment manufacturer).Furthermore, another computer (i.e., controller, server, etc.) canaccess controller 450 to exchange data via at least one of a directconnection, an intranet, or the internet.

Optionally, substrate holder 400 can include an electrode through whichRF power is coupled to plasma in a processing region above substrate410. For example, support base 420 can be electrically biased at an RFvoltage via the transmission of RF power from an RF generator through animpedance match network to substrate holder 400. The RF bias can serveto heat electrons to form and maintain plasma, or bias substrate 410 inorder to control ion energy incident on substrate 410, or both. In thisconfiguration, the system can operate as a reactive ion etch (RIE)reactor, where the chamber and upper gas injection electrode serve asground surfaces. A typical frequency for the RF bias can range from 1MHz to 100 MHz and is preferably 13.56 MHz.

Alternately, RF power can be applied to the substrate holder electrodeat multiple frequencies. Furthermore, an impedance match network canserve to maximize the transfer of RF power to plasma in the processingchamber by minimizing the reflected power. Various match networktopologies (e.g., L-type, π-type, T-type, etc.) and automatic controlmethods can be utilized.

Referring now to FIG. 6, a substrate holder is described according toanother embodiment. The substrate holder 500 comprises a substratesupport 530 having a first temperature and configured to support asubstrate 510, a temperature-controlled support base 520 positionedbelow substrate support 530 and configured to be at a second temperatureless than the first temperature (e.g. less than a desired temperature ofsubstrate 510), and a thermal insulator 540 disposed between thesubstrate support 530 and the temperature-controlled support base 520.Additionally, the substrate support 530 comprises a center heatingelement 533 (located at a substantially center region below substrate510) and an edge heating element 531 (located at a substantially edge,or peripheral, region below substrate 510) coupled thereto, andconfigured to elevate the temperature of the substrate support 530.Furthermore, the support base 520 comprises one or more cooling elements521 coupled thereto, and configured to reduce the temperature of thesubstrate support 530 via the removal of heat from the substrate support530 through thermal insulator 540.

As shown in FIG. 6, the center heating element 533 and the edge heatingelement 531 are coupled to a heating element control unit 532. Heatingelement control unit 532 is configured to provide either dependent orindependent control of each heating element, and exchange informationwith a controller 550.

Additionally, as shown in FIG. 6, the substrate holder 500 can furthercomprise an electrostatic clamp (ESC) comprising one or more clampingelectrodes 535 embedded within substrate support 530. The ESC furthercomprises a high-voltage (HV) DC voltage supply 534 coupled to theclamping electrodes 535 via an electrical connection. The design andimplementation of such a clamp is well known to those skilled in the artof electrostatic clamping systems. Furthermore, the HV DC voltage supply534 is coupled to controller 550 and is configured to exchangeinformation with controller 550.

Furthermore, as shown in FIG. 6, the substrate holder 500 can furthercomprise a back-side gas supply system 536 for supplying a heat transfergas, such as an inert gas including helium, argon, xenon, krypton, aprocess gas, or other gas including oxygen, nitrogen, or hydrogen, tothe center region and the edge region of the backside of substrate 510through two gas supply lines, and at least two of a plurality oforifices and channels (not shown). The backside gas supply system 536,as shown, comprises a two-zone (center/edge) system, wherein thebackside pressure can be varied in a radial direction from the center toedge. Furthermore, the backside gas supply system 536 is coupled tocontroller 550 and is configured to exchange information with controller550.

Further yet, as shown in FIG. 6, the substrate holder 500 furthercomprises a center temperature sensor 562 for measuring a temperature ata substantially center region below substrate 510 and an edgetemperature sensor 564 for measuring a temperature at a substantiallyedge region below substrate 510. The center and edge temperature sensors562, 564 are coupled to a temperature monitoring system 560.

Referring now to FIG. 8, a flowchart describing a method 700 ofcontrolling the temperature of a substrate on a substrate holder in aprocessing system is presented according to another embodiment. Forexample, the temperature control scheme can pertain to multiple processsteps for a process in a processing system having a substrate holdersuch as one of those described in FIGS. 1 through 6. The method 700begins in 710 with disposing a substrate on a substrate holder.

The substrate holder comprises a plurality of temperature sensorsreporting at least a temperature at an inner region and an outer regionof the substrate and/or substrate holder. Additionally, the substrateholder comprises a substrate support having a first heating element anda second heating element heating the inner region and the outer regionrespectively, and a support base having a cooling element for coolingthe inner region and the outer region. The first and second heatingelements and the cooling element are controlled by a temperature controlsystem to maintain the substrate holder at a selectable set-pointtemperature. Furthermore, the substrate holder comprises a thermalinsulator disposed between the substrate support and the support base.

In 720, the substrate is set to a first temperature profile. Using thetemperature control system, a first base temperature for the basesupport (that is less than the first temperature profile (e.g. thesubstrate temperature), and a first inner set-point temperature and afirst outer set-point temperature are selected. Thereafter, thetemperature control system adjusts the cooling element and the first andsecond heating elements to achieve the selected temperatures describedabove.

In 730, the substrate is set to a second temperature profile. Using thetemperature control system, a second base temperature for the basesupport, and a second inner set-point temperature and a second outerset-point temperature are selected. Thereafter, the temperature controlsystem changes the substrate temperature from the first temperatureprofile (i.e., first inner and outer set-point temperatures) to thesecond temperature profile (i.e., second inner and outer set-pointtemperatures) by optionally adjusting the cooling element to change thefirst base temperature to the second base temperature and adjusting theinner and outer heating elements until the second inner and outerset-point temperatures are achieved.

In one example, the substrate temperature is increased (or decreased)from the first temperature profile to the second temperature profile,while the second base temperature remains the same as the first basetemperature. The power delivered to the inner and outer heating elementsis increased (or decreased) in order to heat (or cool) the substratefrom the first temperature profile to the second temperature profile.

In another example, the substrate temperature is increased (ordecreased) from the first temperature profile to the second temperatureprofile, while the second base temperature is changed to a valuedifferent from the first base temperature. The power delivered to theinner and outer heating elements is increased (or decreased) in order toheat (or cool) the substrate from the first temperature profile to thesecond temperature profile, while the power delivered to the coolingelement is increased (or decreased) in order to change the first basetemperature to the second base temperature. Thus, according to oneembodiment of the invention, the temperature of the support base isvaried to assist the substrate support in controlling the temperature ofthe substrate. The present inventors have recognized that this varyingof the support base temperature can provide more accurate and/or rapidtemperature transitions of the substrate.

The temperature control system utilizes a control algorithm in order tostably adjust temperature(s) in response to measured values provided bythe temperature monitoring system. The control algorithm can, forexample, include a PID (proportional, integral and derivative)controller. In a PID controller, the transfer function in the s-domain(i.e., Laplacian space) can be expressed as:G _(c)(s)=K _(P) +K _(D) s+K _(I) s ⁻¹,  (1)

where K_(P), K_(D), and K_(I), are constants, referred to herein as aset of PID parameters. The design challenge for the control algorithm isto select the set of PID parameters to achieve the desired performanceof the temperature control system.

Referring to FIG. 7A, several exemplary time traces of temperature areshown to illustrate how different sets of PID parameters lead to adifferent temperature response. In each case, the temperature isincreased from a first value to a second value. A first time trace oftemperature 601 illustrates a relatively aggressive control schemehaving a relatively low value for K_(I), for example, wherein the timetrace exhibits “overshoot” and a series of oscillations following theovershoot. A second time trace of temperature 602 illustrates arelatively less aggressive control scheme having a relatively highervalue for K_(I), for example, wherein the time trace exhibits arelatively slow, gradual increase to the second temperature. A thirdtime trace of temperature 603 illustrates a desired moderatelyaggressive control scheme having a value for K_(I) between that of timetrace 601 and time trace 602, for example, wherein the time traceexhibits a relatively faster increase to the second temperature withoutovershoot. However, the present inventors have recognized that the useof only one PID parameter set is not sufficient to provide a desiredcondition for stability and rise rate.

According to one embodiment, two or more PID parameter sets are utilizedto achieve a rapid and stable adjustment of the temperature between aninitial value and a final value. FIG. 7B illustrates an exemplary timetrace of temperature 600 utilizing two sets of PID parameters. A firstset of PID parameters is used for a first time duration 622, and asecond set of PID parameters is used for a second time duration 624. Thefirst time duration 622 can be determined by setting a temperatureoffset 620 from the final value of the temperature. For example, thetemperature offset can range from approximately 50% to 99% of thetemperature difference between the initial value and the final value.Additionally, for example, the temperature offset can range fromapproximately 70% to 95% of the temperature difference between theinitial value and the final value, and desirably, the temperature offsetcan range from approximately 80% to 95%.

For example, a relatively aggressive PID parameter set may be used forthe first time duration 622, while a relatively less aggressive PIDparameter set may be used for the second time duration 624.Alternatively, for example, the PID parameter K_(D) can be increasedfrom the first PID set to the second PID set, the PID parameter K_(I)can be decreased from the first PID set to the second PID set, or acombination thereof.

Although only certain embodiments of this invention have been describedin detail above, those skilled in the art will readily appreciate thatmany modifications are possible in the embodiments without materiallydeparting from the novel teachings and advantages of this invention.Accordingly, all such modifications are intended to be included withinthe scope of this invention.

1. A method for controlling the temperature of a substrate in asubstrate processing system, the substrate processing system including asubstrate holder for supporting said substrate and having a temperaturesensor reporting a temperature at a region of said substrate and aheating element heating said region, said heating element beingcontrolled by a temperature control system to control the temperature ofsaid substrate using a PID control algorithm, the method comprising:selecting a first set-point temperature; selecting a second set-pointtemperature; selecting a first PID parameter set including a firstproportional constant K_(P1), a first integral constant K_(I1) and afirst derivative constant K_(D1); selecting a second PID parameter setincluding a second proportional constant K_(P2), a second integralconstant K_(I2) and a second derivative constant K_(D2); placing saidsubstrate on said substrate holder; adjusting the temperature of saidsubstrate to said first set-point temperature; processing said substratefor a first period of time at said first set-point temperature; changingthe temperature of said region of said substrate from said firstset-point temperature to said second set-point temperature using saidfirst PID parameter set for a first ramp period of time and continuingto change the temperature of said region of said substrate from saidfirst set-point temperature to said second set-point temperature usingsaid second PID parameter set for a second ramp period of time, saidsecond ramp period of time following said first ramp period of time; andprocessing said substrate for a second period of time at said secondset-point temperature.
 2. The method of claim 1, wherein said changingthe temperature of said region comprises using said first PD parameterset until the temperature change from said first set-point temperatureis equal to or greater than approximately 50% to 99% of the temperaturedifference between said first set-point temperature and said secondset-point temperature.
 3. The method of claim 2, wherein said changingthe temperature of said region comprises using said first PD parameterset until the temperature change from said first set-point temperatureis equal to or greater than approximately 70% to 95% of the temperaturedifference between said first set-point temperature and said secondset-point temperature.
 4. The method of claim 3, wherein said changingthe temperature of said region comprises using said first PID parameterset until the temperature change from said first set-point temperatureis equal to or greater than approximately 80% to 95% of the temperaturedifference between said first set-point temperature and said secondset-point temperature.
 5. The method of claim 1, wherein said selectingsaid second PID parameter set comprises selecting said second derivativeconstant K_(D2) to be greater than said first derivative constantK_(D1).
 6. The method of claim 1, wherein said selecting said second PIDparameter set comprises selecting said second integral constant K_(I2)to be less than said first integral constant K_(I1).
 7. A method forcontrolling the temperature of a substrate in a substrate processingsystem, the substrate processing system including a substrate holder forsupporting said substrate and having a plurality of temperature sensorsreporting at least a temperature at an inner region and an outer regionof said substrate, and first and second heating elements heatingrespectively said inner region and said outer region, said first andsecond heating elements being controlled by a temperature control systemusing a PID controller to maintain said substrate holder at a selectableset-point temperature, the method comprising: selecting a first innerset-point temperature and a first outer set-point temperature; selectinga second inner set-point temperature and a second outer set-pointtemperature; selecting a first inner PID parameter set including a firstinner proportional constant K_(Pinner1), a first inner integral constantK_(Iinner1) and a first inner derivative constant K_(Dinner1); selectinga second inner PID parameter set including a second inner proportionalconstant K_(Pinner2), a second inner integral constant K_(Iinner2) and asecond inner derivative constant K_(Dinner2); selecting a first outerPID parameter set including a first outer proportional constantK_(Pouter1), a first outer integral constant K_(Iouter1) and a firstouter derivative constant K_(Douter1); selecting a second outer PIDparameter set including a second outer proportional constantK_(Pouter2), a second outer integral constant K_(Iouter) and a secondouter derivative constant K_(Douter2); placing said substrate on saidsubstrate holder; heating said inner region of said substrate to saidfirst inner set-point temperature and said outer region of saidsubstrate to said first outer set-point temperature; processing saidsubstrate for a first period of time at said first inner and outerset-point temperatures; changing the temperature of said inner region ofsaid substrate from said first inner set-point temperature to saidsecond inner set-point temperature using said first inner PID parameterset for a first inner ramp period of time and continuing to change thetemperature of said region of said substrate from said first set-pointtemperature to said second set-point temperature using said second innerPID parameter set for a second inner ramp period of time, said secondinner ramp period of time following said first inner ramp period oftime, and changing the temperature of said outer region of saidsubstrate from said first outer set-point temperature to said secondouter set-point temperature using said first outer PID parameter set fora first outer ramp period of time and continuing to change thetemperature of said region of said substrate from said first set-pointtemperature to said second outer set-point temperature using said secondouter PID parameter set for a second outer ramp period of time, saidsecond outer ramp period of time following said first outer ramp periodof time, and processing said substrate for a second period of time atsaid second inner and outer set-point temperatures.
 8. The method ofclaim 7, wherein said first inner set-point temperature is less thansaid second inner set-point temperature, and said first outer set-pointtemperature is less than said second outer set-point temperature.
 9. Themethod of claim 7, wherein said first inner set-point temperature isgreater than said second inner set-point temperature, and said firstouter set-point temperature is greater than said second outer set-pointtemperature.
 10. The method of claim 7, wherein said heating said innerregion of said substrate to said first inner set-point temperaturecomprises heating said inner region of said substrate by couplingelectrical power to an inner resistive heating element, and wherein saidheating said outer region of said substrate to said first outerset-point temperature comprises heating said outer region of saidsubstrate by coupling electrical power to an outer resistive heatingelement.
 11. The method of claim 10, wherein said changing thetemperature of said inner and outer regions of said substrate to saidsecond inner and outer set-point temperatures comprises increasing theelectrical power to said inner resistive heating element and increasingthe power to said outer resistive heating element.
 12. The method ofclaim 10, wherein said changing the temperature of said inner and outerregions of said substrate to said second inner and outer set-pointtemperatures comprises decreasing the electrical power to said innerresistive heating element and decreasing the power to said outerresistive heating element.
 13. The method of claim 7, furthercomprising: clamping said substrate to said substrate holder.
 14. Themethod of claim 13, further comprising: providing a heat transfer gas tothe backside surface of said substrate on said substrate holder.
 15. Themethod of claim 14, further comprising: configuring the upper surface ofsaid substrate holder to have an inner thermal region for supplying afirst heat transfer gas to the backside surface of said substrate and anouter thermal region for supplying a second heat transfer gas to thebackside surface of said substrate; selecting a first inner pressure forsaid inner thermal region and a first outer pressure for said outerthermal region; selecting a second inner pressure for said inner thermalregion and a second outer pressure for said outer thermal region; duringsaid heating, providing a first heat transfer gas to said inner thermalregion at said first inner pressure and a second heat transfer gas tosaid outer thermal region at said first outer pressure; and during saidchanging the temperature of said inner and outer regions of saidsubstrate, providing said first heat transfer gas to said inner thermalregion at said second inner pressure and said second heat transfer gasto said outer thermal region at said second outer pressure.
 16. Themethod of claim 7, wherein said processing said substrate for a firstperiod of time comprises etching a layer of material on said substrate.17. The method of claim 1 wherein said processing said substrate for asecond period of time comprises etching another layer of materialunderlying said layer of material etched during said first period oftime.
 18. A method of changing the temperature of a substrate duringprocessing of the substrate, comprising providing the substrate on asubstrate holder, the substrate holder comprising a temperaturecontrolled substrate support for supporting the substrate, a temperaturecontrolled base support for supporting the substrate support and athermal insulator interposed between the temperature controlledsubstrate support and the temperature controlled base support; settingthe temperature of the base support to a first base temperaturecorresponding to a first processing temperature of said substrate;setting the substrate support to a first support temperaturecorresponding to said first processing temperature of said substrate;setting the temperature of the base support to a second base temperaturecorresponding to a second processing temperature of said substrate; andchanging the substrate support temperature to a second supporttemperature corresponding to said second processing temperature of saidsubstrate, said changing comprising: selecting a first PID parameter setincluding a first proportional constant K_(P1), a first integralconstant K_(I1) and a first derivative constant K_(D1), selecting asecond PID parameter set including a second proportional constantK_(P2), a second integral constant K_(I2) and a second derivativeconstant K_(D2), and changing the temperature of said substrate fromsaid first set-point temperature to said second set-point temperatureusing said first PID parameter set for a first ramp period of time andcontinuing to change the temperature of said substrate from said firstset-point temperature to said second set-point temperature using saidsecond PID parameter set for a second ramp period of time, said secondramp period of time following said first ramp period of time.
 19. Themethod of claim 18, wherein at least one of said first and secondsupport temperatures is a temperature profile that varies across an areaof said substrate support.